Buoy.

An old oar.

Clamp. This solid item is stamped with the name of the old Aylings boatyard in Putney, which was based where Chas Newens Marine now stands.  Boating expert Jim Boyes says: 'it's not clear what the clamp was for, but the two halves would split when you undid the two nuts. Exhaust clamps are very similar on some of today's cars. but back in those days things were made much stronger.'